Tiling
data class Tiling(val matrix: Matrix, val extGState: ExtGState?, val paintType: Int, val tilingType: Int, val bbox: Rectangle, val xStep: Double, val yStep: Double, val contentBytes: ByteArray, val baseColor: RgbColor = RgbColor(0.5, 0.5, 0.5)) : PdfPattern
Tiling pattern (PatternType = 1). The content stream lives in contentBytes; full rendering requires laying out tiles across the filled region. We don't render that yet — callers get the dict description and an opaque grey fallback in baseColor.